From 049c69f5c73ec399311548774a055b3bac6968f9 Mon Sep 17 00:00:00 2001
From: luochunsheng <luochunsheng@huawei.com>
Date: Tue, 9 Apr 2019 20:38:13 +0800
Subject: [PATCH] added check if correct symlink exists

---
 alternatives.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/alternatives.c b/alternatives.c
index cdfec6d..b02cce2 100644
--- a/alternatives.c
+++ b/alternatives.c
@@ -456,6 +456,7 @@ static int removeLinks(struct linkSet * l, const char * altDir, int flags) {
 
 static int makeLinks(struct linkSet * l, const char * altDir, int flags) {
     char * sl;
+    char buf[PATH_MAX];
 
     sl = alloca(strlen(altDir) + strlen(l->title) + 2);
     sprintf(sl, "%s/%s", altDir, l->title);
@@ -463,12 +464,17 @@ static int makeLinks(struct linkSet * l, const char * altDir, int flags) {
 	    if (FL_TEST(flags)) {
 		    printf(_("would link %s -> %s\n"), l->facility, sl);
 	    } else {
-	            unlink(l->facility);
+                    memset(buf, 0, sizeof(buf));
+                    readlink(l->facility, buf, sizeof(buf));
 
-		    if (symlink(sl, l->facility)) {
-			    fprintf(stderr, _("failed to link %s -> %s: %s\n"),
-				    l->facility, sl, strerror(errno));
-			    return 1;
+                    if(strcmp(sl, buf) != 0) {
+                        unlink(l->facility);
+
+                        if (symlink(sl, l->facility)) {
+                            fprintf(stderr, _("failed to link %s -> %s: %s\n"), l->facility,
+                            sl, strerror(errno));
+                            return 1;
+                        }
 		    }
 	    }
     } else
@@ -478,16 +484,21 @@ static int makeLinks(struct linkSet * l, const char * altDir, int flags) {
     if (FL_TEST(flags)) {
 	printf(_("would link %s -> %s\n"), sl, l->target);
     } else {
-	if (unlink(sl) && errno != ENOENT){
-	    fprintf(stderr, _("failed to remove link %s: %s\n"),
-		    sl, strerror(errno));
-	    return 1;
-	}
+        memset(buf, 0, sizeof(buf));
+        readlink(sl, buf, sizeof(buf));
+
+        if(strcmp(l->target, buf) != 0) {
+            if (unlink(sl) && errno != ENOENT) {
+                fprintf(stderr, _("failed to remove link %s: %s\n"), sl,
+                        strerror(errno));
+                return 1;
+            }
 
-	if (symlink(l->target, sl)) {
-	    fprintf(stderr, _("failed to link %s -> %s: %s\n"),
-		    sl, l->target, strerror(errno));
-	    return 1;
+            if (symlink(l->target, sl)) {
+                fprintf(stderr, _("failed to link %s -> %s: %s\n"), sl, l->target,
+                        strerror(errno));
+                return 1;
+            }
 	}
     }
 
-- 
1.8.3.1